It is generally known that between is used for a choice that involves two distinct options, and among for choices that involve more than two items. For example, ‘You need to choose between working on weekends and working on evenings’ and ‘She distributed the toys among the children.’
But matters are not always as simple.
We should use between when talking about distinct, individual items, even if there are more than two of them. For example, ‘An agreement was made between Canada, Mexico, and the United States.’ Here, ‘an agreement was made among…’ is incorrect.
On the other hand, we use among when talking about things that aren’t distinct items. For example, ‘She had the option to choose among the top business schools in the country.’
So, when three or more entities relate to each other individually and equally rather than collectively, or when the relationship is not general but reciprocal, ‘between’ is the correct choice.